Fabrication And Modification Of TiO₂ Nanotube Arrays By Anodic Oxidation Methods

In recent years,Tatanium dioxide(TiO2)nanotubes have received increasing attention due to their non-toxic,anti-corrosion nature,high statibility and excellent photocatalytic performance.During the anodization process,the oxidation time,temperature,voltage and fluoride ions contained in the electrolyte have been considered the most important factor determining the growth of TiO2 nanotubes.This paper systematically investigated the influence of ethylene glycol concentration on the physicochemical properties of TiO2 nanotubes prepared by anodization oxidation.The 2corresponding photocatalytic performances are further investigated by photodecolorization of an organic dye.A seirs of studies have been down on the modification of TiO2 nanotubes in order to improve the large band gap and recombination of the photo-generated e--hole+ pairs.CdO/TiO2 nanotubes,NiO/TiO2 nanotubes and Fe2O3/TiO2 nanotubes were prepared by impregnation and continuous impregnation.The research results indicate that atverylow ethylene glycol concentrations only a nanoporous structured TiO2 oxide layer had a thickness of hundred nanometers can be formed,Within the increasing of ethylene glycol concentration,the pore size gradually increased and the non-corroded parts between the nanopores gradually dissolved,and the nanoporous structure gradually changed into the nanotubes structure.When the large diameter TiO2 nanotube array appears,the oxide thickness increases to about 2 ?m,within increasing ethylene glycol concentration,the pore size of TiO2 nanotubes decreases,and the oxide thickness increases to 4 ?m.The nanotube structure is favor to photocatalytic degradation of rhodamine B.The decrease of diameter of TiO2 nanotubes and the increasing of tube length will decrease the photocatalytic degradation performance.CdO/TiO2 nanotubes were prepared by impregnation method using Cd(NO3)2 as precursor.At low Cd(NO3)2 concentration,the morphology of TiO2 nanotubes not changed,at higher Cd(NO3)2 concentration would be formed nanocrystalline on the surface of TiO2 nanotubes.After modification,Cd2+ was combined with TiO2 forming CdTiO3 which changed the Ti-O bond energy,at suitable Cd(NO3)2 concentration will enhance the photocurrent of TiO2 nanotubes,but further increase the Cd(NO3)2 concentration will reduce the photocatalytic of TiO2 nanotubes,and the electron lifetime has rarely effect on the photocatalytic properties of TiO2 nanotubes.NiO/TiO2 nanotubes was prepared by impregnation method,after impregnation and calcination the surface of TiO2 nanotubes became slightly disorder,at high precursor concertrations would be formed particle cluster on the surface of TiO2 nanotubes.The XRD spectra shows that Ni may enter into TiO2 lattice which resulting the lattice distortion.After irradiation for 120 min under UV light there was no significant difference in the degradation rate of Rhodamine B,but the degradation rate of Rhodamine B was quite different under visible light.Fe2O3/TiO2 nanotubes were prepared by continuous impregnation method,nanoparticles accumulate on the surface of Fe2O3/TiO2 nanotubes which induce the adhesion between nanotubes and decreasing the thickness of the oxide layer.Fe2O3/TiO2 nanotubes also shows the characteristics of n-type semiconductors and ptype semiconductors.The photocatalytic performance shows that the impurity on the surface of TiO2 nanotubes will decreases the photocatalytic performance of TiO2 nanotubes.